"If Christ is not raised...."

"When I use a word," Humpty Dumpty said in a rather a scornful tone,
"it means just what I choose it to mean - neither more nor less."
"The question is," said Alice, "whether you can make words mean different things."
"The question is," said Humpty Dumpty, "which is to be master - that's all."

The definition of "Christianity" is sometimes approached the way Humpty Dumpty used words. There are those who wish to master the word so it will fit them. Albert Mohler responds to "Must one believe in the Resurrection to be a Christian?" at On Faith:

.... Christianity without the literal, physical resurrection of Jesus Christ from the dead is merely one religion among many. "And if Christ is not risen," said the Apostle Paul, "then our preaching is empty and your faith is in vain" [1 Corinthians 15:14]. Furthermore, "You are still in your sins!" [v. 17]. Paul could not have chosen stronger language. "If in this life only we have hope in Christ, we are of all men the most pitiable" [v. 19].

Yet, the resurrection of Jesus Christ has been under persistent attacks since the Apostolic age. Why? Because it is the central confirmation of Jesus' identity as the incarnate Son of God, and the ultimate sign of Christ's completed work of atonement, redemption, reconciliation, and salvation. [....]

As Paul well understood, Christianity stands or falls with the empty grave. If Christ is not raised, we are to be pitied, for our faith is in vain. Those who would preach a resurrectionless Christianity have substituted the truth of the gospel for a lie. But, asserted Paul, Christ is risen from the dead. Our faith is not in vain, but is in the risen Lord. He willingly faced death on a cross and defeated death from the grave. The Resurrection is the ultimate sign of God's vindication of His Son. [more]

R. Albert Mohler Jr.: Resurrection Essential to Christianity - On Faith at washingtonpost.com